Today, from an article about American Sign Language, I learned several things that surprised me. American Sign Language.

1. "Some experts say that it is the fourth-most-common language in the States, after English, Spanish and Chinese."
2. I had thought everything was spelled out, and I feel silly not to have realized it basically relies on signs that repesent a whole word rather that an individual letter. (Question below.)
3. "One prominent misconception about American Sign Language is that it is merely English with signs replacing words. ASL actually has its own structure." (Question below.)
4. Gestures and such cues differ. "People conversing in spoken language often use their hands or the volume of their voice to accent a point. In sign, since the hands are already quite busy and one can't very well sign more loudly or softly, a signer may widen his eyes or squint, move his head forward dramatically or draw his head back slowly to convey a sense of passion, urgency or lack of interest.Facial expressions, body and head movements, and sign placement all play important grammatical roles. A furrowed brow or puckered lips can alter the meaning of a sentence."
5. You can make embarrassing mistakes. "For example, be careful when signing 'coffee,' or else you may unwittingly make an unwanted sexual advance."

Question re #2: Does the sign represent a word or rather a concept, so that foreigners would use the same sign for the same concept? Compare: the symbol '10' represents the same concept to a Frenchman as it does to us, even though he would write its name as 'dix' and we would write it completely differently, as 'ten'.

Question re #3: Can anyone tell me more about the differences, and how they arose? (The article says merely, "Signs for verbs remain the same, no matter their tense, for instance.")

Question re #2: Does the sign represent a word or rather a concept, so that foreigners would use the same sign for the same concept? Compare: the symbol '10' represents the same concept to a Frenchman as it does to us, even though he would write its name as 'dix' and we would write it completely differently, as 'ten'.

Well, different countries have different sign languages. They are mutually unintelligible. ASL has many different dialects, or regionalisms if you prefer. I ran a computer lab in a local high school about 15 years ago, and there were at least 8-19 deaf students who came through at different times (with their interpretors). I talked with them about dialects and how ASL is very different from English. (In fact, there is something called Exact Signed English which many deaf students are taught in public school. This is English with signs/gestures for each word. It is so different from ASL that students have to learn it or ASL as foreign languages essesintally.) FWIW, the Wikipedia article on ASL is pretty good.

Question re #3: Can anyone tell me more about the differences, and how they arose? (The article says merely, "Signs for verbs remain the same, no matter their tense, for instance.")

Well, verbs aren't conjugated for tense, person, number, etc., as in Latin or Spanish. They use other signs for past and future. Signs for pronouns, similar to Chinese.

One fascinating syntactic feature is the pronominal system. You can spell out peoples names at the beginning of a conversation in different locations in front of the signer. Then during the conversation, one simply points to the area to refer to that person.